Vessels for holding high temperature materials, such as molten metal, are typically lined with a material to provide thermal insulation. Proper thermal insulation helps prevent thermal loss, saving energy and reducing the cost associated with preheating vessels. Thermal insulation also helps reduce the wear and tear on the vessel.
Vessels used to transport molten metals often undergo creep deformation caused by long exposure to high temperatures. Because creep increases with temperature, the less efficient the thermal insulation is, the greater the rate of creep will be. This can be a serious problem as the vessel may eventually deform to the point where it can no longer be used for its intended purpose and, in certain cases, deformation of the vessel may result in failure during use, posing a serious safety hazard.
An example of a vessel used to transport high temperature materials is a ladle used in the steelmaking process to transport molten metal from a blast furnace. Because of the high temperature associated with molten metal, the ladle undergoes extreme temperature swings. Over a period of time this results in creep deformation of the ladle's steel shell. The deformation has increased in modern steelmaking since carbon-containing refractory bricks were developed for use as linings in the early 1980s. The molten metal as well as the deformation of the ladle shell deteriorates the ladle brick lining and often leads to cracking and possibly catastrophic failures of both the lining and the shell. Lining a ladle with typical insulation brick can also be a time consuming and expensive task.
Numerous methods and devices have been developed in an attempt to improve the thermal efficiency of holding vessels. One of these methods utilizes a lining made from ceramic insulation board. This method, however, also suffers from drawbacks. Because ceramic insulation boards are typically highly porous, they have a tendency to shrink or abrade during use. This can lead to a loss of compression in the working linings, creating a gap between the bricks, and allow molten metal to penetrate the lining. This greatly reduces the thermal efficiency and can damage the vessel. Additionally, linings have been made by spraying refractory material over consumable insulation boards. The sprayed linings, however, are quickly degraded and must be replenished frequently. This can result in added expensive and a loss of productivity as the vessel is taken out of service to be relined.